Polymeric materials and products made therefrom must exhibit resistance to degradation if they are to be successfully marketed. Degradation can be seen as a partial or total loss of structural integrity, a darkening or discoloration of the product, a loss of flexibility or resilience, or a combination of the above phenomena. These phenomena are promoted or catalyzed by air (oxygen), heat, and light, particularly ultraviolet light.
To protect polymeric materials, ingredients which can be collectively called stabilizers are admixed with the materials to prevent or inhibit degradation. These stabilizers work in diverse and complex ways, such that a compound which stabilizes against heat and oxygen degradation in a polymer may not stabilize against light degradation in the same polymer, or vice versa. Furthermore, a compound which acts as a stabilizer against oxygen degradation in one type of polymeric material may be relatively inactive in another type of polymeric material. Thus, compounds which are stabilizers are further classed as antioxidants, antiozonants, heat stabilizers, and ultraviolet (UV) light stabilizers, depending upon what type of stabilization they demonstrate. In many cases, to obtain optimum protection, a mixture of compounds, each specifically selected to afford maximum protection against a certain type of degradation, is often used.
The present invention is directed to a new class of UV stabilizers. The basic structure of this class is a substituted decahydropuinoline, exemplified in its simplest form as 2,2,4-trimethyldecahydroquinoline. The 2,2,4-trimethyl substituted compound is already known as an antioxidant for rubber, as disclosed in U.S. Pat. Nos. 2,831,861 and 2,998,468. Unfortunately, the compound is not an effective UV stabilizer for rubber. However, it has been unexpectedly discovered that 2,2,4-trimethyldecahydroquinoline is a very effective UV stabilizer for plastics. Furthermore, other novel substituted decahydroquinoline compounds have been prepared which are as good as or better UV stabilizers than the trimethyl substituted compound.
Other art in this area is as follows: U.S. Pat. Nos. 3,362,929; 3,362,930; 3,829,292; 3,901,849; 3,910,918; 3,939,164; and Published patent application Ser. Nos. B402,162 and B571,638; and British Pat. No. 999,806; and an article in the J. Amer. Chem. Soc., Vol. 60 (1938) at page 1458 et seq.